This invention is a protective device for electrical equipment. More particularly, this equipment provides an alarm signal if a piece of rotating equipment stops rotating and it uses essentially no electrical energy unless it is providing an alarm.
Many items of electrical equipment are expected to run with little or no attention for long periods of time and do so successfully. Some of these items of equipment can lead to relatively annoying complications if a brief power interruption or a circuit failure causes the equipment to stop without providing an alarm to alert an operator. In particular this is true of vacuum systems in which a mechanical pump is driven by an electric motor. A power failure affecting a vacuum pump can lead to stalling of the pump or belt damage if the pump is started after power has been restored. If the mechanical pump is a fore pump in a high-vacuum system which includes an oil diffusion pump, then there is an added possibility of oxidation of pump oil when the diffusion pump continues to receive power when the mechanical pump is not maintaining an adequate fore vacuum. Prompt work by an operator who is informed of such operating difficulties can prevent damage to equipment and can lead to the early restoration of proper operation. However, many such installations do not warrant the presence of an operator to watch at all times for such failures. It would be useful to have an inexpensive system to provide an alarm if such a pump stopped. It would be even more advantageous if the system that provided the alarm used no energy except when it was providing the alarm.
It is an object of the present invention to provide an inexpensive alarm system for rotating equipment.
It is a further object of the present invention to provide an alarm for rotating equipment that uses no energy except when the system is stopped and it is desired to produce an alarm.
Other objects will become apparent in the course of a detailed description of the invention.